It is a slippery slope, I agree, showing that most haven't understood to teach properly. (not saying that I'm any different)
But grace is a gift, and God will have mercy on whomever He chooses to have mercy. Yet it would seem to me that you can lose that gift by acting without mercy, yourself.
I don't believe Christ ever said as long as you believe in me, you can go ahead and do whatever you want. Kill, rape, beat my servants, taunt, steal, etc. But at a time when we WERE doing all those things, God still sent His Son to show us the Way, and to be a mediator for us, and to make amends for us. So that we could look to Him, and be saved. That was His gift to us, as I understand things. We didn't do anything to deserve that gift. But now that we have this gift, it is up to us whether we abuse it, toss it away, or embrace it.
Tammy